test_runner: add initial draft for fakeTimers

Signed-off-by: Erick Wendel <erick.workspace@gmail.com>

lib/internal/test_runner/fake_timers.js

@@ -0,0 +1,110 @@
+'use strict';
+
+const {
+  DateNow,
+  SafeMap,
+  Symbol,
+  globalThis,
+} = primordials;
+
+class Timers {
+  constructor() {
+    this.timers = new SafeMap();
+
+    this.setTimeout = this.#createTimer.bind(this, false);
+    this.clearTimeout = this.#clearTimer.bind(this);
+    this.setInterval = this.#createTimer.bind(this, true);
+    this.clearInterval = this.#clearTimer.bind(this);
+  }
+
+  #createTimer(isInterval, callback, delay, ...args) {
+    const timerId = Symbol('kTimerId');
+    const timer = {
+      id: timerId,
+      callback,
+      time: DateNow() + delay,
+      interval: isInterval,
+      args,
+    };
+    this.timers.set(timerId, timer);
+    return timerId;
+  }
+
+  #clearTimer(timerId) {
+    this.timers.delete(timerId);
+  }
+
+}
+
+let realSetTimeout;
+let realClearTimeout;
+let realSetInterval;
+let realClearInterval;
+
+class FakeTimers {
+  constructor() {
+    this.fakeTimers = {};
+    this.isEnabled = false;
+    this.now = DateNow();
+  }
+
+  tick(time = 0) {
+
+    // if (!this.isEnabled) {
+    //   throw new Error('you should enable fakeTimers first by calling the .enable function');
+    // }
+
+    this.now += time;
+    const timers = this.fakeTimers.timers;
+
+    for (const timer of timers.values()) {
+
+      if (!(this.now >= timer.time)) continue;
+
+      timer.callback(...timer.args);
+      if (timer.interval) {
+        timer.time = this.now + (timer.time - this.now) % timer.args[0];
+        continue;
+      }
+
+      timers.delete(timer.id);
+    }
+  }
+
+  enable() {
+    // if (this.isEnabled) {
+    //   throw new Error('fakeTimers is already enabled!');
+    // }
+    this.now = DateNow();
+    this.isEnabled = true;
+    this.fakeTimers = new Timers();
+
+    realSetTimeout = globalThis.setTimeout;
+    realClearTimeout = globalThis.clearTimeout;
+    realSetInterval = globalThis.setInterval;
+    realClearInterval = globalThis.clearInterval;
+
+    globalThis.setTimeout = this.fakeTimers.setTimeout;
+    globalThis.clearTimeout = this.fakeTimers.clearTimeout;
+    globalThis.setInterval = this.fakeTimers.setInterval;
+    globalThis.clearInterval = this.fakeTimers.clearInterval;
+
+  }
+
+  reset() {
+    this.isEnabled = false;
+    this.fakeTimers = {};
+
+    // Restore the real timer functions
+    globalThis.setTimeout = realSetTimeout;
+    globalThis.clearTimeout = realClearTimeout;
+    globalThis.setInterval = realSetInterval;
+    globalThis.clearInterval = realClearInterval;
+  }
+
+  releaseAllTimers() {
+
+  }
+}
+
+module.exports = { FakeTimers };

lib/internal/test_runner/test.js

@@ -31,6 +31,7 @@ const {
   AbortError,
 } = require('internal/errors');
 const { MockTracker } = require('internal/test_runner/mock');
+const { FakeTimers } = require('internal/test_runner/fake_timers');
 const { TestsStream } = require('internal/test_runner/tests_stream');
 const {
   createDeferredCallback,
@@ -108,6 +109,11 @@ class TestContext {
     return this.#test.mock;
   }
 
+  get fakeTimers() {
+    this.#test.fakeTimers ??= new FakeTimers();
+    return this.#test.fakeTimers;
+  }
+
   runOnly(value) {
     this.#test.runOnlySubtests = !!value;
   }

lib/test.js

@@ -31,3 +31,20 @@ ObjectDefineProperty(module.exports, 'mock', {
     return lazyMock;
   },
 });
+
+let lazyFakeTimers;
+
+ObjectDefineProperty(module.exports, 'fakeTimers', {
+  __proto__: null,
+  configurable: true,
+  enumerable: true,
+  get() {
+    if (lazyFakeTimers === undefined) {
+      const { FakeTimers } = require('internal/test_runner/fake_timers');
+
+      lazyFakeTimers = new FakeTimers();
+    }
+
+    return lazyFakeTimers;
+  },
+});

test/parallel/test-runner-fake-timers.js

@@ -0,0 +1,46 @@
+'use strict';
+const common = require('../common');
+process.env.NODE_TEST_KNOWN_GLOBALS = 0;
+
+const assert = require('node:assert');
+const { fakeTimers, it, mock, afterEach, describe } = require('node:test');
+describe('Faketimers Test Suite', () => {
+
+  describe('setTimeout Suite', () => {
+    afterEach(() => fakeTimers.reset());
+
+    it('should advance in time and trigger timers when calling the .tick function', (t) => {
+      fakeTimers.enable();
+
+      const fn = mock.fn(() => {});
+
+      global.setTimeout(fn, 4000);
+
+      fakeTimers.tick(4000);
+      assert.ok(fn.mock.callCount());
+    });
+
+    it('should advance in time and trigger timers when calling the .tick function multiple times', (t) => {
+      fakeTimers.enable();
+      const fn = mock.fn();
+
+      global.setTimeout(fn, 2000);
+
+      fakeTimers.tick(1000);
+      fakeTimers.tick(1000);
+
+      assert.strictEqual(fn.mock.callCount(), 1);
+    });
+
+    it('should keep setTimeout working if fakeTimers are disabled', (t, done) => {
+      const now = Date.now();
+      const timeout = 2;
+      const expected = () => now - timeout;
+      global.setTimeout(common.mustCall(() => {
+        assert.strictEqual(now - timeout, expected());
+        done();
+      }), timeout);
+    });
+
+  });
+});